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January 22, 2012

Sunset from 30,000 Feet

Sunset from 30,000 feet

There is nothing quite like a spectacular sunset. Seeing one from cruise in an airplane seems to make it just a little bit more amazing. I took this photo in November 2008 somewhere over northern Mexico. The bands of color are just spectacular.

The reason the sky is all those fancy colors is actually the same reason that the sky is blue most of the time. It is caused by a property of light called scattering. Radio waves come in lots of different frequencies, each with a different station broadcasting it. The different frequencies mean a different number of waves passing by each second, and since it is traveling at the speed of light, that means that as the frequency changes, the length of the wave changes too.

The exact same thing happens with light too. In fact, radio waves are light, just at a frequency that our eyes cannot detect. Visible light is just a little section of the electromagnetic spectrum. Within that little bit of the spectrum, the wavelengths vary, red being long waves, and violet being short waves.

As light comes into the atmosphere it starts hitting air and dust. Since each color's wavelength is different, some of the colors are able to go around the particles because the waves are bigger than the particle, but others hit the particles and sort of bounce around the sky from molecule to molecule. Blue light bounces around a ton, and comes towards our eyes from every direction, so we see lots of blue. Red, on the other end of the spectrum doesnt hit a lot of things, and just passes right by most stuff, so there it is only coming directly from the sun.

When the sun sets, it is sort of going around the corner of the earth, so the light has to come a lot further through the atmosphere, and so more of the red light gets reflected, so we see lots of red around the sum. In this picture you can see all the colors in order, red, then orange, yellow, green is sort of smushed into yellow, then blue.